This invention relates generally to electrical connectors, and, more specifically, to surface mount header assemblies for mating engagement with plug assemblies.
The mating of a plug assembly into a receptacle assembly to form a connector assembly often involves a high insertion force. This is particularly true when the connector comprises mating connector housings containing many contacts. For example, automobile wiring systems, such as power train systems, typically include electrical connectors. Typically, each electrical connector includes a plug assembly and a header assembly. The plug assembly is mated into a shroud of the header assembly. The header assembly is in turn mounted on a printed circuit board. Each of the plug assembly and the header assembly typically includes a large number of electrical contacts, and the contacts in the header assembly are electrically and mechanically connected to respective contacts in the plug assembly when the header assembly and the plug assembly are engaged. To overcome the high insertion force to connect the plug assembly into the header assembly, an actuating lever is sometimes employed to mate contacts of the plug assembly and the header assembly.
Surface mount header assemblies provide a number of advantages over through-hole mounted header assemblies. In addition to offering cost and process advantages, surface mounting allows for a reduced footprint for the header assembly and thus saves valuable space on a circuit board or permits a reduction in size of the circuit board. When the header assembly is surface mounted to a circuit board, solder tails extend from one side of the header assembly in an angled manner for surface mounting to a circuit board, and also extend substantially perpendicular from another side of the header assembly for mating engagement with contacts of the plug assembly. In one automotive connector system, fifty two contacts are employed in one version of the header assembly, and the large number of contacts presents manufacturing and assembly challenges in fabricating the header assembly, as well as installation problems during surface mounting of the header assembly to the circuit board.
For example, it is desirable for surface mounting that the solder tails of the header assembly are coplanar to one another for mounting to the plane of a circuit board. Achieving coplanarity with a large number of contact pins, however, is difficult due to manufacturing tolerances over a large number of contacts. Sometimes additional solder paste is utilized to compensate for tolerances of the contacts or for misalignment of the pin contacts during assembly of the header. Over a large number of header assemblies, however, the incremental cost of the increased amount of solder paste per header assembly can be significant, and non-planarity of the pin contacts with respect to the plane of the circuit board may negatively affect the reliability of the header assembly. Additional solder paste thickness can also cause solder bridging problems for other surface mount components on fine pitch or may require different stencils to be used. Depending upon the degree of non-planarity of the solder tails, some of the contacts may be weakly connected or not connected to the circuit board at all, either of which is an undesirable and unacceptable result.
Furthermore, the high insertion forces during engagement and disengagement of the header assembly and the plug assembly may be detrimental to the soldered connections of the header assembly. To prevent the soldered connections from being broken, a solder clip is sometimes used which is soldered to the circuit board at the corners of the header. As such, the mechanical connection of the solder clips incur the brunt of mechanical strain as the header assembly is mated and unmated from a mating connector. Tolerances in manufacturing the solder clips, however, introduce additional non-planarity issues when the header assembly is soldered to a circuit board. At one end of the tolerance range, the solder clips may prevent the contacts from fully contacting the circuit board, which may impair the quality of the soldered connections of the contacts. At the other end of the tolerance range, the solder clips may not fully contact the circuit board during soldering, which may impair the ability of the solder clips to spare the contacts from large insertion and extraction forces as the header assembly is engaged and disengaged from a mating connector.